The invention relates to a heat exchanger, in particular an exhaust gas heat exchanger, heat exchanger, having a fluid channel, such as a tube or multiplicity of tubes, like a tube array, through which a first medium, such as exhaust gas, can flow, and a second fluid channel, such as a housing, through which a second medium, such as a coolant, can flow, the ends of the tube array being connected to the tube plates, for example in a cohesive manner, and the tube plates being connected to the housing, for example in a cohesive manner.
Such a heat exchanger as an exhaust gas heat exchanger has been disclosed by DE-A 199 07 163 from the applicant. In this known design, the ends of a tube array are accommodated in appropriate openings in a tube plate and are welded to the tube plate. The tube array with the two tube plates is arranged in the housing, the tube plates being welded circumferentially to the shell of the housing. Thus, the tubes are firmly connected to the housing via the tube plate, which can lead to thermal stresses under certain conditions. Hot exhaust gas flows through the tubes on the inside and colder coolant flows on the outside and also washes around the inside of the housing. In particular in the case of relatively long tube lengths of such an exhaust gas heat exchanger, for example for commercial vehicles, the different expansions of tubes and housing shell can lead to stresses which are no longer permissible, which can result, for example, in destruction of the tube-plate connection.
It is therefore an object of the invention to improve an exhaust gas heat exchanger of the type mentioned at the beginning to the effect that thermal stresses on account of different expansions are reduced or avoided, so that the heat exchanger achieves the service life which is normal in motor vehicles.